feat: Migrate to HttpClient5 in `OAuth2Service` #2271

Job	Run time
Collect Context	3s
Run CodeQL Analysis	5m 8s
Check Formatting	28s
Run BlackDuck Scan	-1s
Run Security Rating	-1s
Test ${{ matrix.task.archetype }} Archetype	0s
Run ${{ matrix.task.name }} Analysis	0s
Build	-1s
Test	0s
	5m 36s

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